The present invention relates generally to document image systems, and more particularly to a document scanner system having a magnetically levitated carriage.
Scanners for electronically forming an image of an original are known. Typically, the captured image provided by a scanner is a pixel data array that is stored in memory in a digital format. A distortion-free image requires a faithful mapping of the original image to the pixel data array. Scanners typically include at least one means for imposing a mechanical constraint during the image capture process in order to maximize the likelihood of faithful mapping.
The four types of scanners known in the art are drum scanners, flatbed scanners, two-dimensional array scanners and hand scanners. The focus of this invention is the flatbed scanner.
Flatbed scanners include a linear array sensor that is moved relative to the original along an axis that is perpendicular to the axis of the array. Thus, the position of the sensor in one dimension may be known by tracking the relative movement of the sensor. The position of the sensor in the perpendicular direction is implicitly fixed by addressing a particular array element at which intensity is to be measured.
In one embodiment of the flatbed scanner, the original is placed on a transparent platen and the sensor, along with an image illumination source, is placed on a side of the platen opposite to the original. As long as the original is not moved relative to the platen, the pixel data array will be fixed with respect to the image to be captured.
In another embodiment, the original is moved, rather than the sensor. This second embodiment is typical of facsimile machines. Precision paper transports provide a high degree of positional accuracy during the image-capture process.
Flatbed scanners use cables or straps to move the sensor carriage along rails that guide the carriage through the scan swath. This configuration can lead to maintenance and reliability issues in the long term. It is also subject to wide variations in scan results. If the carriage is not able to move in a smooth predictable fashion, the scan results will be of poor quality. The position information currently collected is an approximation collected by the motor “dragging” the scan carriage across the field of the platen. Any hesitation caused by cable fatigue or transport rail wear will result in degraded quality of the scan results.
Beneficial aspects of flatbed scanners include the ability to accommodate documents at least as large as A4, or 8.5″×11″ paper. Moreover, some of these scanners can handle A1 paper in a single setup. However, the scanners are not generally portable, since they require a host computer for control, data storage and image manipulation.
Thus, a need still remains for a scanner carriage mechanism that is not subject to the wear and maintenance of today. In view of the popularity and business need to scan information for archival or transmission purposes, it is increasingly critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.